The present invention relates to the field of Electric-Discharge Machining (EDM) drill and more particularly to an unproved EDM drill capable of selectively operating in a hole drilling and thread tapping mode.
A conventional EDM drill comprises with machining axis (i.e., Z axis), rotation axis (i.e., R axis), dielectric supply (pump) device, round tube electrode, guide, dielectric filtering system, control unit, and an EDM power supply. In performing EDM drilling, firstly R axis is rotated in a constant speed or adjustable speed, and pump to supply dielectric through rotate spindle into tubing electrode, then electrode tube through the guide. At the same time machining axis servo feed and EDM power are activated to perform an EDM drilling on a work piece. Such EDM drill can drill a hole with a very small diameter and deep, for example like 0.5 mm drill into 100 mm depth of work piece, the diameter to depth ratio is 1:200 (i.e., smaller diameter to depth ratio as compared to other mechanical drills). Further, the alignment of the drilled hole is good. Hence, such high speed EDM drills have been widely used. Such as conductive metal material is capable of performing by EDM drill irrespective of their hardness. Unfortunately, such high efficiency and precision equipment is applicable to hole drilling only.
Conventionally, thread making devices may use following three broad categories: (1) Mechanical tapping devices (the most widely used ones). In detail, firstly a hole is drilled into a work piece by drill. Then drive tapper to perform a thread tapping. Typically, the work piece is formed of soft material, i.e., a heat treatment (e.g., hardening) has not been performed thereon. In one example, a carbide tapper is used for tapping a hardened material. However, the tapper may be broken while machining. (2) Computer numerical control (CNC) EDM based tapping devices. In detail, rotation axis (i.e., C axis) and machining axis (i.e., Z axis) of a CNC EDM die sinker are interpolated servo feed with thread pitch of thread electrode and the activation of EDM power for performing an EDM tapping. However, such technique is only applicable to a device having a rotation axis (i.e., C axis or fourth axis), otherwise the following one is applicable. (3) Mounting an orbiting device on a conventional EDM die sinker. In detail, firstly, drill a hole on a work piece. Then drive a thread electrode into the hole. Finally, turn on the EDM power to electrode, supply dielectric fluid and orbiting the electrode to perform a thread by EDM machining. The drawbacks of this technique are that it is manually operated. Further, at least two types of tapping devices are required for machining the work piece into an acceptable one. This inevitably increases cost and it is inefficient. Thus improvement exists.
It is therefore an object of the present invention to provide a combination hole drilling and thread tapping Electric-Discharge Machining (EDM) capable of selectively operating in a hole drilling mode and thread tapping mode. The EDM drill machine comprises with a rotation axis (as R axis) driven by the servo motor; machining axis (as Z axis) driven by the another one servo motor being capable of switching between a default mode and a servo following mode for realizing a spark feed; and a thread electrode extended down from the R axis through a guide; wherein a dielectric supply and the R axis rotates for performing the EDM tapping on the work piece. The invention has a plurality of configurations.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.